This study will compare the emergence (as measured by time to extubation) and recovery profiles of remifentanil and fentanyl when administered as part of a balanced anesthetic technique with halothane or sevoflurane. Additionally, the response to surgical stress (e.g. placement of mouth gag and excision of tonsils) will be compared in pediatric patients undergoing tonsilectomy with or without adenoidectomy surgery. Safety of remifentanil and fentanyl will be compared when they are administered as part of a balanced anesthetic technique with halothane or sevoflurane.